The present invention relates to modules for hermetically sealing integrated circuits and more particularly to metallization of the parts of the module for superior sealing.
The present invention provides an improved method and device for improving the reproducibility and reliability of hermetically sealing modules for a microcircuit package by forming an improved solder joint. FIG. 1 which will be described in more detail hereinafter, shows the outside dimensional relationships of the metallized ceramic cover being designed to be the same as that of the sealing frame of the microcircuit package. Additionally, in the prior art, the metallized area on the ceramic cover was restricted to be only on that surface area mating with the base member.
As applied in particular to ceramic modules for microcircuits such as integrated or monolithic integrated circuits, a first thin layer of refractory metal such as tungsten or a mixture of molybdenum and manganese which forms a bond with the ceramic when subjected to the atmosphere and high temperatures in a dry hydrogen furnace is deposited. A second layer of metal such as nickel or copper is then deposited in order to improve solderability. A third top layer of gold plating is often deposited in a dry inert atmosphere in order to assure solderability without the use of flux.
In the prior art, the metallized ceramic cover is solder sealed to the frame of the microcircuit package by sandwiching a solder preform between the metallizations and then melting the preform. The heat to melt the solder is applied by running the assembly through the hot zone of a belt furnance or by applying a heated platen to the face of the ceramic cover. Disadvantages of this design are that the solder flow and wetting does not occur as planned, and the results cannot be positively determined by visual examination. Additionally, the solder melting methods are limited to those described hereinabove which can subject the microcircuit assembly to excessive amounts of heat.
Accordingly, it is desirable to provide a metallization for hermetic sealing of modules which overcomes the above-stated difficulties.
In view of the above, it is an object of the present invention to provide means for achieving formation of a superior hermetic seal for ceramic modules overcoming the above-stated difficulties.
Further objects and advantages of the present invention will become apparent as the following description proceeds and features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.